Process for Controlling Cyst Nematode Population in Soybeans

ABSTRACT

A method of controlling cyst nematode population in soybeans by providing a blended composition of soybean varieties. At least one of the soybean varieties in the blend has resistance to a given race spectrum, while another of the soybean varieties in the blend may have resistance to a differing race spectrum or be a susceptible variety. The blend may include 10 to 90% of the first variety and 90 to 10% of the second variety. The blend may consist of three or more soybean varieties.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 09/207,350 filed Dec. 8, 1998 and U.S. patent application Ser. No. 09/689,809 filed Oct. 13, 2000 which are both hereby incorporated by reference and which contained disclosure from and claims the benefit under Title 35 United States Code §119(e) of U.S. Provisional Application Ser. No. 60/075,299, filed Feb. 20, 1998 and entitled “Process for Controlling Cyst Nematode Population in Soybeans”, hereby incorporated by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

AUTHORIZATION PURSUANT TO 37 C.F.R. §1.71 (d) (e)

A portion of the disclosure of this patent document, including appendices, may contain material which is subject to copyright protection. The copyright owner has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of soybean production, and more particularly to a method of controlling cyst nematode population in soybeans.

2. Description of the Related Art

Cyst nematodes are responsible for direct loss in soybean yield, and indirect losses due to cost of pesticides and non-optimal use of land or rotation. Soybean cyst nematodes (Heterodera glycines) have a negative economic impact that may exceed $500 million per year in the United States.

Economically significant densities of cyst nematodes usually cause stunting of crop plants. The root system is smaller than for uninfected plants, resulting in leaves showing symptoms of mineral deficiencies with an increased risk of wilting in dry soil conditions. Yield losses are related to the density of cyst nematode present at planting and in severe cases may be substantially above 50% for crops such as soybeans.

Current control methods include the use of chemicals, cultural techniques, and the use of resistant soybean varieties. Nematicides are considered to present significant health risks and cultural control such as crop rotation may be unacceptable to specialist growers or growers with few alternative crops.

Use of resistant soybean varieties does not provide adequate long-term control since cyst nematode race shift occurs. For example, if race 3 is present in a field and the farmer plants a race 3 resistant variety, within one year race shift occurs, i.e., race 3 mutates (race shifts) to race 1, 2, 4, etc. Therefore, the same race 3 resistant soybean variety is again susceptible to the new race spectrum of cyst nematode. Furthermore, cyst nematode is capable of race shifting at a rate faster than the industry can breed or engineer resistant varieties with high yields.

Those concerned with these and other problems recognize the need for an improved process for controlling cyst nematode population in soybeans.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a method of controlling cyst nematode population in soybeans by providing a blended composition of soybean varieties. At least one of the soybean varieties in the blend has resistance to a given race, while another of the soybean varieties in the blend may be resistant to a race or be a susceptible variety. The blend may include 10 to 90% of the first variety and 90 to 10% of the second variety. The blend of the present invention may also include three or more soybean varieties. Planting the blended composition controls cyst nematode by forcing them into a dormant state, or by maintaining a specific race consistency that can be controlled in a field environment.

DETAILED DESCRIPTION OF THE INVENTION

The following Examples describe a process to control cyst nematode race shift and/or to force CN (cyst nematode) to become dormant by blending varieties of soybeans in the following combinations:

1. CN race resistant soybean variety+CN race resistant soybean variety;

2. CN race resistant soybean variety+CN race susceptible soybean variety;

3. CN race resistant genetically altered soybean variety+CN race resistant genetically altered soybean variety;

4. CN race resistant genetically altered soybean variety+CN race susceptible genetically altered soybean variety;

5. any other blend of soybean varieties for the express purpose of high yielding soybean varieties; and

6. combinations as explained below.

The following table provides an explanation of codes used in the examples and Tables 31 and 32. TABLE 1 Explanation of codes: SOURCE OF SCN VARIETY RESISTANCE: RESISTANT TO: A = PI88788 Race 3 & 4 B = PEKING Race 1 & 3 C = PI437654 Hartwig/Race 1, 2, 3, 4 & 5 D = PI209332 Race resistant E = Susceptible Unknown F = Unknown race resistant Unknown source G = NSG Race 3 & 14

Definitions

In the description and tables which follow, a number of terms are used. In order to provide a clear and consistent understanding of the specification and claims, including the scope to be given such terms, the following definitions are provided:

Resistant: As used herein, “resistant” or resistance means a soybean variety that is resistant to one or more races of Soybean Cyst Nematode (SCN). Where SCN attach to a resistant variety a majority of the nematodes die and/or do not reproduce.

Susceptible: As used herein, “susceptible” means a soybean variety susceptible to all races of Soybean Cyst Nematode. When SCN attach to a susceptible variety, the nematodes grow larger and reproduce.

Soybean Cyst Nematode (SCN): As used herein, “SCN” is a microscopic roundworm that attaches to soybean roots.

Cyst Nematode Race Spectrum: As used herein, “race spectrum” means a soybean variety having resistance to one or more races of SCN (i.e., spectrum of races).

Soybean Cyst Nematode Number (SCN #): As used herein, the “SCN #” is the number of SCN eggs per 100 cc of soil taken from the area adjacent to the soybean plant.

Transverse Blends: The reversal of a known or stated blend. Example: (90%) A×(10%) B if transgressed would be: (10%) A×(90%) B, or any other combination of stated varieties in any and all percentages between 10% and 90%.

CTA Soybean Blend: As used herein, a “CTA Soybean Blend” is a blend of seed of one or more SCN resistant soybean varieties with one or more susceptible soybean varieties.

CTB Soybean Blend: As used herein, a “CTB Soybean Blend” is a blend of seed of two or more SCN resistant soybean varieties.

Rotating: As used herein, “rotating” (rotation) means changing the soybean blend or crop planted from season to season on the same field. For example, a CTA soybean blend is planted in the first year, a CTB soybean blend is planted in the same field in the second year, corn (an alternate crop) is planted in the third year, a CTA blend is planted the fourth year, etc. Various soybean blends, individual SCN resistant and susceptible soybean varieties, and any alternate crop can be rotated from one growing season to the next in a given field.

EXAMPLES

The following examples are provided to further illustrate the present invention and are not intended to limit the invention beyond the limitations set forth in the appended claims.

Examples of resistant varieties of soybeans that could be used in lieu of the varieties identified in Table 1 are included as defined by brand name and maturity group in Table 32.

Examples of susceptible varieties of soybeans that could be used in lieu of the varieties identified in Table 1 are included as defined by brand name and maturity group in Table 33.

The present invention provides for a method of blending soybean varieties. In one preferred embodiment the blend consists of two or more varieties resistant to SCN (i.e., CTB). In another preferred embodiment the blend consists of one or two resistant varieties blended with a susceptible variety (i.e., CTA). The blend of the present invention may contain 10% to 90% of a first soybean variety and 90% to 10% of a second variety. In another preferred embodiment, two resistant varieties are blended with one susceptible variety where the blend contains 10% to 50% of a first resistant variety, 10% to 50% of a second resistant variety and 5% to 40% of a susceptible variety.

The blends produced by the method of the present invention result in 1) improved control and reduction of SCN number in the field and/or 2) improved yield compared versus the same varieties per se.

Example 1 Example Blends of Resistant and Susceptible Soybean Varieties

(90%)A X (10%)E (90%)B X (10%)E (90%)C x (10%)E (80%)A X (20%)E (80%)B X (20%)E (80%)C x (20%)E (70%)A X (30%)E (70%)B X (30%)E (70%)C x (30%)E (60%)A X (40%)E (60%)B X (40%)E (60%)C x (40%)E (90%)D X (10%)E (90%)F X (10%)E (90%)G X (10%)E (80%)D X (20%)E (80%)F X (20%)E (80%)G X (20%)E (70%)D X (30%)E (70%)F X (30%)E (70%)G X (40%)E (60%)D X (40%)E (60%)F X (40%)E (60%)G X (40%)E *Any and all other blends. *Any and all other blends of stated varieties in any and all combinations of percentages.

Example 2 Blends of Resistant and Resistant Soybean Varieties

**(90%)A X (10%)B **(90%)B X (10%)A **(90%)C X (10%)A **(80%)A X (20%)C **(80%)B X (20%)C **(80%)C X (20%)B **(70%)A X (30%)D **(70%)B X (30%)D **(70%)C X (30%)D **(60%)A X (40%)F **(60%)B X (40%)F **(60%)C X (40%)F **All Transverse **All Transverse **All Transverse blends blends blends **(90%)A X (10%)A **(90%)D X (10%)A **(80%)B X (20%)B **(80%)D X (20%)B **(70%)C X (30%)C **(70%)D X (30%)F **(60%)D X (40%)D **60%)D X (40%)C **(50%)E X (50%)E **All Transverse **(40%)F X (60%)F blends **All Transverse **(90%)G X (10%)A blends **(80%)G X (20%)B **(90%)F X (10%)A **(70%)G X (30%)C **(80%)F X (20%)B **(60%)G X (40%)D **(70%)F X (30%)C **(60%)G X (40%)F **(60%)F X (40%)D **All Transverse **All Transverse blends blends *Any and all other blends. *Any and all other blends of stated varieties in any and all combinations of percentages. **Example of Transverse blend: (90%)A X (10%)B Transversed: (10%)A X (90%)B, or any other combination of stated varieties in any and all percentages.

Example 3 Blends of Resistant+Resistant×Susceptible Soybean Varieties:

**(90%)(A + B) X **(90%)(B + C) X **(90%)(C + D) X (10%)E (10%)E (10%)E **(80%)(A + C) X **(80%)(B + C) X **(80%)(C + F) X (20%)E (20%)E (20%)E **(70%)(A + D) X **(70%)(B + F) X **(70%)(C + G) X (30%)E (30%)E (30%)E **(60%)(A + F) X **(60%)(B + G) X **(60%)(C + B) X (40%)E (40%)E (40%)E *Any and all other *Any and all other *Any and all other blends blends blends **All Transverse **All Transverse **All Transverse blends blends blends **(90%)(D + F) X **(90%)(A + A) X (10%)E (10%)E **(80%)(F + D) X **(80%)(B + B) X (20%)E (20%)E **(70%)(D + C) X **(70%)(C + C) X (30%)E (30%)E **(60%)(D + G) X **(60%)(D + D) X (40%)B (40%)E *Any and all other **(50%)(F + F) X blends (50%)E **All Transverse **(40%)(G + G) X blends (60%)E *Any and all other blends **All Transverse blends *Any and all other blends of stated varieties in any and all combinations of percentages. **Example of transverse blend: (90%)A X (10%)B Transgressed: (10%)A X (90%)B, or any other combination of stated varieties in any and all percentages.

Example 4 Resistant & Susceptible Blend=A×E

Percentage 80% 20% Variety Type Example A E Stated Variety MRK 97CN33 MRK 9829 Appendix A B

Example 5 Resistant & Resistant Blend=A×A

Percentage 50% 50% Variety Type Example A A Stated Variety MRK 95CN27 MRK 97CN33 Appendix A A

Example 6 Resistant & Resistant & Susceptible Blend=(A+A)×E

Percentage 40% 40% 20% Variety Type Example A A B Stated Variety MRK 95CN27 MRK97CN33 MRK 9829 Appendix A A B

Example 7 Resistant & Susceptible Blend=C×E

Percentage 60% 40% Variety Type Example C E Stated Variety Dwight MRK 9826 Appendix A B

Example 8 Resistant & Resistant Blend=G×A

Percentage 60% 40% Variety Type Example G A Stated Variety Hornback HBK58 LG Seed JMS5009C Appendix A A

Example 9 Resistant & Resistant & Susceptible Blend=(C+G)×E

Percentage 30% 40%) 30% Variety Type Example C G E Variety Hartwick Hornback HBK58 MRK EX835 Appendix A A B

Example 10

The following Tables 2-9 summarize data from field trials conducted in the 1998 growing season on infested and non-infested plots. The variety or blend is listed in the first column. In the second column, SCN resistant (R) and susceptible (S) is identified for each variety and blend. Columns 3-6 are plant height, lodging score, bushels/acre and Kg/hectare respectively. Column 7 shows the initial (early season) SCN # eggs/100 cc soil. Column 8 shows the final (late season or after harvest) SCN # eggs per 100 cc soil. Column 9 shows the % change in SCN#. TABLE 2 Kanawha INFESTED Variety Trial Egg/100 c.c. soil SCN # SCN # % Entry SCN Height (in) Lodging Bu/acre Kg/hectare (initial) (final) Chg 98CN26 R 33.5 1.0 41.5 2434 7775 2875 −271 97CN29 R 32.8 1.6 46.7 2737 3750 1967 −191 98CN26-7 50% R 35.0 1.0 42.2 2473 6100 1475 −414 98CN26CTB 50% R Mean R 32.7 1.8 40.1 2352 5564 2498 Group II Resistant Mean Group II S 30.9 1.7 34.5 2023 6450 5825 Susceptible

As shown in Tables 2 and 3, a blend of two (2) resistant varieties were compared to each of the two (2) resistant varieties, 98CN26 and 97CN29, which were not blended. In Table 2 unexpectedly there was a greater reduction in SCN number with the blend of two resistant varieties.

Varieties Tested: 98CN26 resistant variety - not a blend 97CN29 resistant variety - not a blend 98CN26-7 resistant variety x resistant variety: 98CN26 (60%) x 97CN29 (40%)

As shown in Table 4, unexpectedly the 40% susceptible and 60% resistant blended variety 9829 CTA had equal or higher yield compared to the two resistant varieties or the susceptible variety and had a lower SCN number than resistant variety 98CN30. TABLE 3 Kanawha NONINFESTED Variety Trial Egg/100 c.c. soil SCN # SCN # Entry SCN Height (in) Lodging Bu/acre Kg/hectare (initial) (final) 98CN26 R 40.3 1.0 46.1 2700 NA NA 97CN29 R 38.0 1.5 53.2 3115 NA NA 98CN26-7 50% R 44.0 1.5 52.1 3051 NA NA 98CN26CTB 50% R Mean Group II R 37.9 1.8 53.2 3116 NA NA Resistant Mean Group II S 36.8 1.9 53.8 3153 NA NA Susceptible

TABLE 4 Ames INFESTED Variety Trial Egg/100 c.c. soil SCN # SCN # % Entry SCN Height (in) Lodging Bu/acre Kg/hectare (initial) (final) Change 9829 S 30.8 1.0 52.4 3068 1575 5138 +327 98CN30 40% S 41.0 1.6 54.2 3175 1725 2800 +163 9829CTA 60% R 98CN30 R 40.0 1.5 46.4 2718 3937 9675 +246 Mean R 36.1 2.0 55.5 3250 2484 1733 Group II Resistant Mean S 35.8 2.1 49.6 2907 2231 4563 Group II Susceptible Mean R 43.5 2.1 53.4 3126 2467 2150 Group III Resistant Mean 5 39.1 1.8 49.3 2891 1400 6194 Group III Susceptible

TABLE 5 Ames NONINIFESTED Variety Trial Egg/100 c.c. soil SCN # SCN # Entry SCN Height (in) Lodging Bu/acre Kg/hectare (initial) (final) 9829 S 39.3 1.3 64.8 3794 NA NA 98CN30-9 40% S 46.5 1.5 60.7 3556 NA NA 9829CTA 60% R 98CN30 R 48.3 2.3 60.9 3569 NA NA Mean Group II R 43.3 2.5 61.4 3596 NA NA Resistant R Mean Group II S 41.4 2.5 61.2 3586 NA NA Susceptible Mean Group III R 49.3 2.5 58.3 3419 NA NA Resistant Mean Group III S 44.7 2.0 58.6 3432 NA NA Susceptible

TABLE 6 Crawfordsville INFESTED Variety Trial Egg/100 c.c. soil SCN # SCN # Entry SCN Height (in) Lodging Bu/acre Kg/hectare (initial) (final) 9829 S 19.8 1.1 23.6 1379 5825 NA 97CN33-9 R 25.5 1.0 29.8 1747 7600 NA 98CN30 R 20.0 1.0 18.9 1103 3550 NA 97CN33 R 25.0 1.0 30.5 1785 4625 NA Mean Group II R 22.4 1.1 25.6 1501 5960 NA Resistant Mean Group III R 26.1 1.1 32.9 1925 5377 NA Resistant Mean Group III S 20.9 1.0 20.5 1203 4833 NA Susceptible

TABLE 7 Crawfordsville NONINFESTED Variety Trial Egg/100 c.c. soil SCN # SCN # Entry SCN Height (in) Lodging Bu/acre Kg/hectare (initial) (final) 9829 S 26.3 1.4 44.8 2627 NA NA 97CN33-9 R 37 1.4 48.5 2843 NA NA 98CN30 R 34.3 1.4 49.2 2881 NA NA 97CN33 R 32.8 1.3 43.4 2543 NA NA Mean Group II R 33.5 1.7 47.1 2762 NA NA Resistant Mean Group III R 36.2 1.5 47.9 2806 NA NA Resistant Mean Group III S 34.5 1.6 45.3 2651 NA NA Susceptible

As shown in Table 8, for each of the SCN resistant varieties not blended, there was a decrease in the final count of the SCN infestation. The 98CN26 showed a decrease of 270%, and 97CN29 had 190% decrease. Unexpectedly, in the blended variety, the final count decreased 413% which was significantly greater than in either of the un-blended varieties. This indicates a greater ability to control the SCN infestation through blending.

Ames Infested Variety Trial

Varieties Tested: 9829 susceptible variety - not a blend 98CN30 resistant variety - not a blend 98CN30-9 resistant variety x susceptible variety: 98CN30 (60%) x 9829 (40%)

TABLE 8 Kanawha INFESTED Variety Test Egg/100 c.c. soil Ht Kg/ SCN # SCN # Increase Decrease Entry SCN (in) Lodging Bu/Acre Hectare (initial) (final) (%) (%) 98CN26 R 33.5 1 41.5 2434 7775 2875 270.43% 97CN29 R 32.8 1.6 46.7 2737 3750 1967 190.65% 98CN26-7 R + R 35 1 42.2 2473 6100 1475 413.56% 98CN26CTB

As shown in Table 9, a blend of one (1) resistant variety 98CN30 and one (1) susceptible variety 9829 is compared versus each of the blend components separately.

As expected, the susceptible variety demonstrated a dramatic increase (326%) in the final SCN count, while the resistant variety showed moderate increase (245%). Unexpectedly, the final SCN count in the blended bean, 98CN30-9 (9829CTA), showed a significantly lower SCN number increase of 162%. Therefore, showing an overall lower infestation and the ability to control populations.

In addition, the blended soybean, 98CN30-9 unexpectedly showed the most desirable traits of increasing or maintaining yield, while having the least increase of Cyst Nematode populations. TABLE 9 Ames INFESTED Variety Test Egg/100 c.c. soil Height Kg/ SCN # SCN # Increase Decrease Entry SCN (in) Lodging Bu/Acre Hectare (initial) (final) (%) (%) 9829 S 30.8 1.0 52.4 3068 1575 5138 326.22% 98CN30-9 R + S 41.0 1.6 54.2 3175 1725 2800 162.32% 9829CTA 98CN30 R 40.0 1.5 46.4 2718 3937 9675 245.75%

Both Tables 8 and 9 variety trials show the blended soybeans have an enhanced ability to control cyst nematode population.

The method of the present invention is believed to work on cyst nematode by either forcing them into a dormant state, or by blending the soybeans together in a way that enables the farmer to maintain a specific race that can then be controlled in a field environment, such as a blend of race resistant and race susceptible.

The purpose of blending resistant varieties of one (1) race with a resistant variety of another race, or resistant varieties of one (1) race with a susceptible variety may allow the farmer to eliminate cyst nematode and/or place them in a dormant state, and/or maintain race consistency of a controllable type within the field.

One major advantage of this technique is that it is no longer necessary to plant continuous corn, or to continually change soybean varieties as the CN mutates, or race shifts. Additionally, this technology controls the SCN rather than try to keep up with the race shifts as in the past.

Example 11

In another embodiment of the present invention, CTA (Cyst Tech® Level A), CTB (Cyst Tech® Level B) and alternate crops such as corn and alfalfa are rotated in subsequent growing seasons for a given field. CTA is a blend of both resistant and susceptible soybean varieties. CTB is a blend of resistant varieties for one or more SCN races. Unexpectedly, rotation of CTA and CTB has resulted in improved yields and/or reduced counts of soybean cyst nematode (SCN). This unexpected result indicates cyst populations are controlled more effectively when using the method of the present invention versus planting conventional cyst resistant soybeans for two or more generations. When planting conventional resistant soybean varieties the soybean cyst nematode race shifts to a new resistant race. In the method of the present invention Cyst Tech(& Level A (CTA) controls the cyst race in one or more growing seasons, and then by rotating with Cyst Tech® Level B (CTB) in a succeeding growing season, this gives an unexpected result of a reduced SCN population (SCN count) for all races of SCN.

In another embodiment of the present invention, CTA is rotated with CTB in alternate years (or growing seasons). For example, Cyst Tech® Level A (CTA) is planted the first year, while Cyst Tech® Level B (CTB) is planted on the same land the following year. This rotation can be repeated over a number of growing seasons. In another example, CTA is grown for two or more consecutive seasons followed by growing CTB for one or more seasons. Alternatively, corn or another alternate crop can periodically be rotated with soybeans as shown in Table 10, columns 3-8. The rotation of CTA, CTB and an alternate crop can be used in any combination; including the examples shown in Table 10. The determination of whether CTA, CTB or an alternate crop is grown in the next growing season is based on current year data on soybean yield, plant health and appearance, SCN counts versus previous years data and the use of specific SCN resistant varieties in previous years. In one preferred embodiment, a lower SCN count, predominantly a SCN Race 3 environment is obtained to produce higher soybean yields. TABLE 10 Examples of Rotation Patterns Year 2 3 4 5 6 7 8 1 CTA CTB CTA CTB CTA CTB Corn 2 CTB Corn CTA Corn CTB Corn CTA 3 CTA CTB Corn CTA CTB Corn CTA 4 CTB Corn CTA Corn Corn CTA CTA 5 CTA CTA CTB CTA CTB CTA CTA 6 CTB Corn Clover CTA CTA CTB Corn 7 CTA CTB CTA CTB CTA Clover CTA

The method of the present invention includes all possible rotation patterns for growing CTA and CTB and all rotation patterns for growing CTA and CTB with an alternative crop. The alternative crops are primarily non-host crops to SCN, including: corn, forages, sorghum, oats, rye, canola, sunflowers, cotton, rice and any other crop species.

In a preferred embodiment of the present invention, a CTB variety is grown for one season, followed by at least one season of growing a CTA variety. The CTB variety reduces the SCN count, as shown in Example 13, while the CTA variety maintains a lower SCN count versus a resistant line per se as shown in Example 12. Rotating the CTB variety, followed by the CTA variety, results in a predominantly SCN Race 3 environment. A predominantly SCN Race 3 environment generally aids in the expression of high soybean yields.

Example 12

As shown in Table 11, soybean variety MRK9829CTA is compared versus two commercial varieties. MRK9829CTA is a blend of MRK9829 and MRK98CN30. Unexpectedly, the CTA variety, (which is a blend of 60% resistant MRK98CN30 and 40% susceptible soybean variety MRK9829) had a higher yield and a smaller increase in Final SCN count versus the resistant and the susceptible varieties per se. CTA varieties have shown 3 distinct advantages versus commercial varieties. 1) CTA varieties reduce SCN race shift over one or more seasons; 2) CTA varieties had improved control over cyst populations and 3) CTA varieties maintain a higher yield versus conventional commercial varieties in the presence of cyst-infected fields.

The SCN initial count is taken prior to or early in the growing season and the SCN final count is taken late in the growing season or after harvest. TABLE 11 SCN # SCN # SCN # Plant Bushels/ KG per (Initial (Final Increase Variety SCN Height Ldg Acre Hectare Count) Count) (%) MRK9829 S 30.8 1.0 52.4 3068 1575 5138 326.22% MRK9829CTA 40% S 41.0 1.6 54.2 3175 1725 2800 162.32% 60% R MRK98CN30 R 40.0 1.5 46.4 3937 3937 9675 245.75%

Based on the results in Table 11, this environment is a non-race 3 environment, where varieties resistant to SCN race 3 have been previously grown.

Example 13

As shown in Table 12, soybean blend MRK98CN26CTB is compared to SCN resistant varieties MRK97CN29 and MRK98CN26. MR98CN26CTB (CTB) is a blend of 40% MRK97CN29 and 60% MRK98CN26. Unexpectedly the CTB variety had a 414% decrease in SCN count when compared to the other two resistant varieties. CTB varieties show two distinct advantages, including: 1) CTB varieties had improved control over the SCN population; and 2) CTB varieties maintain high yields consistent with non-cyst infected fields as shown in Table 2. As shown in Table 12, CTB varieties reduced cyst count significantly versus the other individual varieties per se.

The SCN initial count is taken prior to or early in the growing season and the SCN final count is taken late in the growing season or after harvest.

Based on the results in Table 12, this environment is a predominantly race 3 environment, where varieties susceptible to Race 3 SCN were previously grown. TABLE 12 SCN # SCN # Plant Bushels/ KG per (Initial (Final % Variety SCN Height Ldg Acre Hectare Count) Count) Change MRK97CN29 R 32.8 1.6 46.7 2737 3750 1967 190.65% MRK98CN26 R 33.5 1.0 41.5 2434 7775 2875 270.43% MRK98CN26CTB 50% R 35.0 1.0 42.2 2473 6100 1475 413.56% 50% S

For example, in another embodiment of the present invention, by rotating MRK9829CTA with MRK98CN26CTB over two or more growing seasons, this results in a higher yielding soybean environment and/or a decrease in the final SCN count.

In Tables 13 through 30, columns 1-3 show the first variety, % of variety, and if the variety is SCN resistant or susceptible. If the percent in column 2 equals 100%, then this is not a blend but the variety listed in column 1 per se. Columns 4, 5 and 6 show the second variety name, if a blend, the percent of the variety 2 in the blend and the SCN resistance or susceptibility respectively. Columns 7 and 8 show the SCN #1 value which is the first SCN count taken earlier in the growing season, the second SCN count (SCN #2) which is the SCN count taken later in the season. Column 9 shows the percent change in SCN count from SCN #1 to SCN #2 and equals SCN #2 divided by SCN #1. Column 10 shows the yield of the variety in bushels per acre.

2002 Data Perry, IA

TABLE 13 Blend % Variety 1 % SCN Variety 2 % SCN SCN #1 SCN #2 Change Bu/A RR0221 100 S  5200 15840 +205 44.45 RR0221CTA-1 40 S RR022SCN 60 R 13260  5160 −257 46.08 RR0022 100 R

TABLE 14 Blend % Variety 1 % SCN Variety 2 % SCN SCN #1 SCN #2 Change Bu/A RR0023 100 S 7020 7860 12 48 RR0023CTA-1 40 S RR0022SCN 60 R 5120 4280 −120 6249 RR0022SCN 100 R

TABLE 15 Blend % Variety 1 % SCN Variety 2 % SCN SCN #1 SCN #2 Change Bu/A RR0125 100 R 9780 3480   −281 50.1 RR0125CTB-1 60 R RR0026SCN 40 R 7080 1640   −432 62.29 RR0125CTB-2 60 R RR9923SCN 40 R 6420 320 −2006 64.03 RR0125CTB-4 60 R RREX26SCN 40 R 7500 120 −6250 61.57 RR0125CTB-5 60 R RR0125SCN 40 R 12240  360 −3400 51

TABLE 16 Blend % Variety 1 % SCN Variety 2 % SCN SCN #1 SCN #2 Change Bu/A RR0225 100 6960 6240  −10 47.24 RR0225CTA 40 S RR0125SCN 60 R 2960  800 −370 52.94 RR0125 100 R 9780 3480 −281 50.1

TABLE 17 Blend % Variety 1 % SCN Variety 2 % SCN SCN #1 SCN #2 Change Bu/A RR0025 100 S 7440 12960    74 41.99 RR0025CTA-1 40 S RREX0126SCN 60 R 4000 2320 −172 41.38 RR0025CTA-2 40 S RREX0126SCN 60 R 7620 4560 −167 63.91 RR0025CTA-3 40 S RREX26SCN 60 R 8220 1040 −790 56.84 RR025CTA-4 40 S RR0125SCN 60 R 6000 4040 −149 56.21 RR0125SCN 100 R 9780 3480 −281 50.1

TABLE 18 Blend % Variety 1 % SCN Variety 2 % SCN SCN #1 SCN #2 Change Bu/A RR0126 100 S 7220 7080   2 59.02 RR0126CTA 40 S RR0125SCN 60 R 6420 1360 −472 65.84 RR0126CTA-1 40 S RREX0125SCN 60 R 12480 2640 −473 52.35 RR0126CTA-2 40 S RR0026SCN 60 R 5520 4080 −135 54.77 RR0126CTA-4 40 S RR0229SCN 60 R 8160 1600 −510 80.23 RR0126CTA-5 40 S RR9927SCN 60 R 7500 4120 −182 55.95 RR0125 100 R 9780 3480 −281 50.1

TABLE 19 Blend % Variety 1 % SCN Variety 2 % SCN SCN #1 SCN #2 Change Bu/A RR0226 100 S 2880 4680 63 51.71 RR0226CTA-3 40 S RR0026SCN 60 R 4920 5760 17 63.91

TABLE 20 Blend % Variety 1 % SCN Variety 2 % SCN SCN #1 SCN #2 Change Bu/A RR26 100 S 6240 13320  +214 44.64 RR26CTA 40 S RREX0126SCN 60 R 12480  9600 −130 49.26 RR26CTA-1 40 S RR0026SCN 60 R 3840 1600 −240 51.36 RR26CTA-2 40 S RREX26SCN 60 R 4200 2080 −202 40.06 RR26CTA-4 40 S RR9927SCN 60 R 5880 3120 −188 58.61 RR26CTA-3 40 S RR0229SCN 60 R 3720 3560 −104 5392 RR26CTA-6 40 S RR0029SCN 60 R 7200 2600 −277 69.03

TABLE 21 Blend % Variety 1 % SCN Variety 2 % SCN SCN #1 SCN #2 Change Bu/A RR9927 100 S 3660 3780    3 52.00 RR9927CTA 40 S RR0229SCN 60 R 4920 3540  −139 58.00 RR9927CTA-1 40 S RR9927SCN 60 R 8520  680 −1253 61.25 RR9927CTA-2 40 S RR0028SCN 60 R 8400 2160  −389 51.69 RR9927CTA-3 40 S RR0128SCN 60 R 8760 9480    8 58.65 RR9927CTA-5 40 S RR0126SCN 60 R 9120 1200  −760 58.43

TABLE 22 Blend % Variety 1 % SCN Variety 2 % SCN SCN #1 SCN #2 Change Bu/A RR0029CTB 50 R RR0028SCN 50 R 14980 1800 −832 55.38 RR0029CTB-1s 50 R RR0029SCN 50 R 3480 1600 −218 65.08 RR0029CTB-2 50 R RR0129SCN 50 R 6540 920 −711 66.27 RR0029CTB-3 50 R RR0128SCN 50 R 9480 1560 −608 59.94

TABLE 23 Blend % Variety 1 % SCN Variety 2 % SCN SCN #1 SCN #2 Change Bu/A RR0129CTB 60 R RR0028SCN 40 R 3800 1560 −244 63.05 RR0129CTB-1 60 R RR0128SCN 40 R 10800 950 −1137 65.6 RR0129CTB-2 60 R RR0029SCN 40 R 3880 880 −441 59.73 RR0129CTB-3s 60 R RR0129SCN 40 R 18960 4120 −460 54.35 RR0129CTB-4 60 R RREX32ASCN 40 R 7800 1440 −542 61.25

TABLE 24 Blend % Variety 1 % SCN Variety 2 % SCN SCN #1 SCN #2 Change Bu/A RR0231 100 S 3720 6600 77 47.12 RR0231CTA-1 40 S RREX32SCN 60 R 4200 1920 −219 56.77 RR0231CTA-2 40 S RR0033SCN 60 R 3080 2040 −151 68.52 RR0231CTA-3 40 S RR0133SCN 60 R 8040 3240 −248 47.19 RR0231CTA-4 40 S RR9933SCN 60 R 2840 3300 16 60.55

TABLE 25 Blend % Variety 1 % SCN Variety 2 % SCN SCN #1 SCN #2 Change Bu/A RREX32ACTB 60 R RR0029SCN 40 R 5160 3300 −156 62.35 RREX32ACTB-1 60 R RR0129SCN 40 R 7620 2200 −346 63.86 RREX32ACTB-2 60 R RR0033SCN 40 R 6480 1380 −470 64.6 RREX32ACTB-3 60 R RR0133SCN 40 R 24960 12840 −194 52.96 RREX32ACTB-4 60 R RR9933SCN 40 R 12000 13080 9 59.77 RREX32ACTB-5s 60 R RREX32ASCN 40 R 4680 4800 3 60.76

TABLE 26 Blend % Variety 1 % SCN Variety 2 % SCN SCN #1 SCN #2 Change Bu/A RR0133CTB 60 R RR0029SCN 40 R 8400 1520 −553 48.72 RR0133CTB-1 60 R RR0129SCN 40 R 3792 1400 −271 42.26 RR0133CTB-2 60 R RR0033SCN 40 R 4200 2680 −157 60.62 RR0133CTB-3s 60 R RR0133SCN 40 R 3280 2000 −164 43.68

TABLE 27 Blend % Variety 1 % SCN Variety 2 % SCN SCN #1 SCN #2 Change Bu/A RR9933CTB 60 R RR0029SCN 40 R 4740 3360 −141 63.89 RR9933CTB-1 60 R RR0129SCN 40 R 4620 440 −105 56.1 RR9933CTB-2 60 R RR0033SCN 40 R 27120 7440 −365 62.59 RR9933CTB-3s 60 R RR9933SCN 40 R 27360 3180 −860 59.18 RR9933CTB-4 60 R RR0133SCN 40 R 15600 3300 −473 57.45

TABLE 28 Blend % Variety 1 % SCN Variety 2 % SCN SCN #1 SCN #2 Change Bu/A RR0033CTB 60 R RR0029SCN 40 R 3960 2160 −1356 57.17 RR0033CTB-1 60 R RR0129SCN 40 R 2360 2040 −116 59.71 RR0033CTB-2s 60 R RR0033SCN 40 R 3540 1600 −347 60.97 RR0033CTB-3 60 R RR0133SCN 40 R 15120 7200 −581 49.04 RR0033CTB-4 60 R RREX35SCN 40 R 4200 1480 −413 59.64

TABLE 29 Blend % Variety 1 % SCN Variety 2 % SCN SCN #1 SCN #2 Change Bu/A RR9934 100 S 960 2600 59 46.87 RR9934CTA-1 40 S RR0033SCN 60 R 1800 1080 −167 53.65 RR9934CTA-2 40 S RR0133SCN 60 R 3720 3060 −122 50.9 RR9934CTA-4 40 S RREX35SCN 60 R 30480 6350 −479 47.96

TABLE 30 Blend Variety % Variety 1 % SCN 2 & 3 % SCN SCN #1 SCN #2 Change Bu/A RREX3CTA 20 S RR0029 40 R 35760 9600 −373 55.86 RR0028 40 R RREX3CTA 20 S RREX32A 40 R 11280 6360 −177 59.09 BSM RR9933 40 R RREX#CTB 20 S RREX32A 40 R 3960 3760 −105 58.2 BSM RR9933 40 R

Example 14

An example of the rotation method of the present invention is shown in Table 31. TABLE 31 Year Variety Eggs/100 cc soil Bu/Acre 1998 Susceptible 20,000  30 1999 9527CTB 5,000 50 2000 Corn 2001 9927CTA 2,000 52

In 1998 a resistant variety was grown in a field in Onawa, Iowa. As shown in Table 31, the SCN# in the field was measured at 20,000 and the variety yielded 30 bu/acre. In 1999 a CTB variety 9527CTB was planted in this same field in Onawa, Iowa. Unexpectedly, in the fall of 1999, the SCN# dropped to 5,000 and also the bushels per acre increased to 50 bu/acre. Corn was grown on this land the following year in 2000. In 2001, a CTA variety 9927CTA was grown, which unexpectedly reduced the SCN# to 2,000 and increased the yield to 52 bushels/acre. In this field, the method of the present invention had resulted in both an increased yield and a reduction in the SCN number.

Examples of SCN resistant soybean varieties are shown in Table 32. Examples of SCN susceptible soybean varieties are shown in Table 33. “NSG” indicates that the seed company did not provide the source for the SCN resistance. “RR” indicates that this variety is a “Roundup Ready” variety in addition to being SCN resistant. (Roundup Ready is a registered trademark of Monsanto Chemical Company). TABLE 32 Brand/Variety Source of SCN Resistance RESISTANT VARIETIES MATURITY GROUP I Great Lakes GL 1559 P188788 Hy-Vigor Jazz P188788 Latham 352 CN P188788 Novartis (NK) P188788 Pioneer 9182 P188788 Prairie PB 156 CN P188788 Prairie PB 188 CN P188788 ProfiSeed PS 197 N P188788 (Public, IL) Bell P188788 (Public, MN) Freeborn P188788 (Public, MN) Faribault P1209332 Stine 1882 P188788 RESISTANT VARIETIES MATURITY GROUP II AgriPro AP 2601 SCN P188788 AgriPro AP 2901 SCN P188788 AgVenture AV-1294 NSG Asgrow A2540 P188788 Asgrow A2869 P188788 Asgrow AG2901 (RR) P188788 & Peking Callahan 4277 NSG Callahan 6299 NSG Coop 199N NSG Dairyland DSR 296 N P188788 DeKalb CX 235 C P188788 DeKalb CX 260 C P188788 DeKalb CX 292 C P188788 Diener Bros DB 926 C P188788 Diener Bros DB 272 C P188788 Diener Bros DB 280 C P188788 Diener Bros DB 2900 CR (RR) NSG Garst D267N P188788 Golden Harvest H-1286 P188788 Great Lakes GL 2533 N P188788 Great Lakes GL 2912 N P188788 Griffith PL 2885 NSG Growmark FS HS 2711 P188788 Growmark FS HS 2951 P188788 Gutwein 7282 C NSG Gutwein 7284 C NSG Henkel SS NBC MSG Hy-Vigor Braxton P188788 Kaltenberg KB 258 N P188788 Kruger K 2220 SCN P188788 Latham 522 CN P188788 Latham 722 CN P188788 LG Seeds LG 6296 C P188788 Mark MRK97 CN-22 P188788 Mark MRK95 CN-27 P188788 Merschman Osage III SCN P188788 Merschman Cherokee VIII P188788 Midwest G-2162 N P188788 Midwest G-2520 N P188788 221 C P188788 MWS 262 C P188788 MWS 270 CN P188788 MWS 291 CN P188788 Mycogen 5291 P188788 NC + 2N18 P188788 NC + 2N87 P188788 Novartis (NK) S29-11 P188788 Patriot 210 N P188788 Patriot 262 N P188788 Pioneer 9234 Peking Pioneer 92B91 P188788 Prairie PB 215 CN P188788 Prairie PB 221 CN P188788 Prairie PB 299 CN P188788 Profiseed PS 227 N P188788 Profiseed Z 465 N P188788 Profiseed PS 2465 N Peking (Public, IL) Jack P188788 (Public, IL) Dwight P188788 (Public, IA) IA 2036 P188788 Roeschley 8246 C NSG Sieben SS 282 N P188788 Stine 2472 P188788 Stine 2972 P188788 Sun Ag SAS 2812 NSG Sunstar 2994 CN P188788 Tri County Stockdale GA 2797 P188788 Trilser Trisoy 2812 NSG UAP Seed DG 3227 N P188788 UAP Seed DG 3281 N P188788 Wilken 2441 N P188788 Wilken 2571 CN P188788 Wilken 2681 P188788 Wilson 2100 SCN P188788 RESISTANT VARIETIES MATURITY GROUP III Adler 305 NSG AgraTech AT 333 P188788 AgraTech AT 345 P188788 AgraTech AT 350 P188788 AgraTech AT 39 RR P188788 AgriPro Ap 3601 SCN P188788 AgVenture AV 1335 NSG AgVenture AV 1351 NSG Asgrow A 3134 P188788 Asgrow AG 3301 RR P188788 & Peking Asgrow A 3431 P188788 & Peking Asgrow A 3559 P188788 Asgrow AG 3701 RR P188788 & Peking Asgrow A 3732 P188788 Asgrow A 3904 STS P188788 & Peking Baird Seed B-3292 NSG Beck 334 P188788 Beck 3440 RR P188788 Beck 382 CN P188788 Berg.-Taylor BT 386 C P188788 Berg.-Taylor BT 398 CR (RR) P188788 Berg.-Taylor BT 399 C P188788 Brown Arise 336-C NSG Brown Arise 375-C NSG Brown Arise 378 C NSG Brown Arise 398 C NSG Midland 8394 N (RR) NSG Midland 8395 N (RR) NSG Callahan 7331 Peking Callahan 337 N P188788 Callahan 7388 P188788 Campbell 327 N NSG Campbell 383 N NSG Crows 33004 P188788 Dairyland DSR 325 P188788 Dairyland DSR 373 P188788 Dairyland DSR 371 RR P188788 DeKalb CX 339 C P188788 DeKalb CX 340 C P188788 DeKalb CX 394 C P188788 Diener Bros DB 329 C P188788 Diener Bros DB 359 C P188788 Diener Bros XB 936 STS P188788 Diener Bros DB 369 P188788 Diener Bros DB 3850 CR (RR) P188788 Fontanelle F 3376 NSG Garst D 358 P188788 Gateway 373 P188788 Golden Harvest H-1337 P188788 Golden Harvest-H 1365 P188788 Golden Harvest X-390 RR P188788 Good Buddy GB 30 C p188788 Great Heart G-395 C P188788 Great Heart GT-398 C RR NSG Great Lakes GL 3434 P188788 Griffith PL 3305 NSG Growmark HS RT 316 (RR) P188788 Growmark 327 N P188788 Growmark HS 3361 P188788 Growmark HS 3471 P188788 Growmark 359 N P188788 Growmark HS 3411 P188788 Growmark 377 N P188788 Growmark HS 3961 P188788 Growmark HS 3971 P188788 Growmark FS HS 3971 P188788 Gutwein 7323 C NSG Gutwein 7350 C NSG Gutwein 7393 C NSG Hoblit HB333 P188788 Hubner 337 N NSG Hubner 351 N NSG Hubner 357 N NSG HyVigor 333 P188788 IMC V346 NSG IMC V373 NSG IMC V395 NSG Kitchen KSC 329 C NSG Kitchen KSC 332 C NSG Kruger K 3444 SCN P188788 Lewis 334 NSG Lewis 3500 STS NSG Lewis 367 C NSG Lewis 362 NSG Lewis 388 NSG Lewis 3800 NSG Lewis 391 NSG Lewis 3901 NSG LG Seeds LG 6343 C P188788 LG Seeds LG 6355 C RR P188788 LG Seeds LG 6384 C P188788 LG Seeds LG 6399 C RR P188788 Mark MRK97 CN-33 P188788 Merschman McKinley II P188788 & Peking MFA Morsoy 538 P188788 Midwest G-3660 N P188788 Midwest G-3720 N P188788 Midwest G-3922 N RR P188788 Midwest X-96400N P188788 Moweaqua MS 336 NSG Moweaqua MS 361 NSG Moweaqua MS 376 NSG Moweaqua MD 8395 (RR) NSG Munson 335-3 NSG MWS 301 CN P188788 MWS 323 C P188788 MWS 340 CN P188788 MWS 362 C P188788 Mycogen 5331 P188788 Mycogen 5376 P188788 NC + 3N55 RR P188788 NC + 3A96 P188788 Novartis (Ciba) 3376 P188788 Novartis (NK) S 39-11 P188788 Patriot 311 N NSG Patriot 331 N P188788 Patriot 332 N P188788 Patriot 356 N NSG Patriot 372 N P188788 Patriot 379 N P188788 Patriot 383 N P188788 Pioneer 93B11 P188788 Pioneer 9362 P188788 Pioneer 9363 (RR) P188788 Pioneer 93B83 P188788 Prairie PB 303 CN P188788 Prairie PB 383 CN P188788 (Public, IL) Cartter P188788 (Public, IL) Pana P188788 (Public, IL) Saline P188788 (Public, IL) Fayette P188788 (Public, IL) Maverick P188788 (Public, IL) Linford P188788 (Public, IL) Yale P188788 (Public, MO) Maverick P188788 (Public, MO) Saline P188788 (Public, IA) IA 3005 P188788 Quality Q 355C NSG Reeds Brand 355 SCN P188788 Roeschley 8372C NSG Schneider S336C NSG Schneider S366C NSG Schneider S379C NSG Schultz 3315 N NSG Schultz 3815 N NSG Excel 9391 N RR NSG Scott's Columbo II NSG Scott's Concorde NSG Scott's Cyster STS NSG Scott's Excel 8391 N RR NSG Stewart SB 3099 P188788 Stewart SB 3799 P188788 Stewart SB 3899 P188788 Stine 3272 P188788 Stone SE-3301 NSG Sun Ag SAS 3172 NSG Sunstar 3230 CN P188788 Sunstar 3590 CN P188788 Terra TS 325 Peking Terra TR 390 SCN NSG Trisler Trisoy 3210 NSG Trisler Trisoy 3342 NSG Trisler Trisoy 3716 NSG Trisler Trisoy 3744 NSG Trisler Trisoy 3867 RR NSG UAP Seed DG 3331 N P188788 UAP Seed DG 3378 N P188788 VanHorn VH 335 N NSG VanHorn VH 376 N NSG VanHorn VH 387 N NSG Wildy WS EX 32087 NSG Wildy WS 3508 NSG Wildy WS EX 37036 NSG Wilken 3431 CN P188788 Wilson 3330 SCN P188788 RESISTANT VARIETIES MATURITY GROUP IV Agra Tech AT 425 P188788 Agra Tech AT 460 P188788 AgriPro AP 4001 SCN P188788 AgriPro HY 4540 SCN P188788 AgriPro HY 458 SCN P188788 AgVenture AV 1445 NSG Asgrow A 4138 P188788 Asgrow AG 4401 RR P188788 & Peking Asgrow AG 4501 RR & STS P188788 & Peking Asgrow 4601 RR P188788 & Peking Asgrow 4604 STS P188788 Asgrow AG 4701 RR P188788 & Peking Asgrow AG 4702 RR P188788 & Peking Asgrow A 4715 P188788 & Peking Asgrow AG 4901 RR P188788 & Peking Asgrow A 4922 P188788 Beck 454 P188788 Beck 460 RR P188788 Berg.-Taylor BT 408 CR (RR) P188788 Berg.-Taylor BT 428 C P188788 Berg.-Taylor BT 436 C P188788 Berg.-Taylor BT 468 CR (RR) P188788 Berg.-Taylor BT 445 C P188788 Brown Arise 418 C NSG Brown Arise 427 C NSG Brown Arise 435 C NSG Midland 8471 N (RR) NSG Brown Arise 498 C NSG Callahan 6435 P188788 Callahan 6440 P188788 Callahan 7467 P188788 Crows 45002 P188788 DeKalb CX 420 C P188788 DeKalb CX 450 C P188788 DeKalb CX 469 C P188788 DeKalb CX 470 C P188788 DeKalb CX 499 C P188788 Diener Bros DB 404 C P188788 Deiner Bros DB 442 C P188788 & Peking Deiner Bros DB 4650 CR (RR) P188788 Deiner Bros DB 4620 CR (RR) P188788 Deiner Bros DB 472 C P188788 Gateway 425 P188788 Gateway 441 P188788 Gateway 451 P188788 Gateway 481 P188788 Gateway 493 Peking Golden Harvest H-1432 P188788 Golden Harvest H-1454 P188788 Golden Harvest H-1487 P188788 Good Buddy GB 402 C P188788 Great Heart G-424-C P188788 Great Heart G-465 C P188788 Great Lakes GL 4548 P188788 Growmark HS 4161 P188788 Growmark HS 4110 P188788 Growmark HS 4161 P188788 Growmark HS 4426 P188788 Growmark RT 446 (RR) P188788 Growmark HS 4801 Peking Gutwein 7439 C NSG Hartz H 4994 P188788 Hartz H 4994 (RR) P188788 Hartz H 4998 (RR) P188788 Hornbeck HBK 4600 NSG Hornbeck HBK 4755 NSG Hornbeck SB HBK R4898 (RR) NSG Hornbeck HBK 49 NSG IMC V443 NSG IMC V455 NSG Kitchen KSC 402 C NSG Lewis 405 NSG Lewis 431 NSG LG Seeds LG 6437 C P188788 LG Seeds LG 6462 C P188788 Merschman Richmond IV P188788 Merschman Houston IV NSG Merschman Memphis III P188788 MFA Morsoy 4067 SCN P188788 MFA Morsoy 444 SCN P188788 Midwest G-4014 N P188788 Midwest G-4320 N P188788 Mycogen 429 P188788 NC + 4A27 P188788 NC + 4N78 RR P188788 Novartis (NK) S 46-44 P188788 Novartis S 46-W8 P188788 Patriot 412 N P188788 Patriot 420 N P188788 Patriot 442 N P188788 Patriot 452 N Peking & P188788 Patriot 457 N P188788 Patriot 482 N P188788 Pioneer 94B01 (RR) P188788 Pioneer 94B41 (RR) P188788 Pioneer 9451 P188788 Pioneer 9481 P188788 Pioneer 9492 (RR) P188788 (Public, IN) Bronson P188788 (Public, SIU) Nile Peking (Public, SIU) Pyramid Peking & P188788 (Public, SIU) Pharaoh Peking (Public, SIU) Egyptian Peking (Public, MO) Delsoy 4210 P188788 (Public, MO) Mustang P188788 (Public, MO) Delsoy 4500 Peking (Public, MO) Avery Peking & P188788 (Public, MO) Delsoy 4710 P1209332 & Peking (Public, MO) Delsoy 4900 Peking (Public, TN) TN 4-86 P188788 (Public, TN) TN 4-94 P188788 & Peking Reeds Brand 350 SCN Peking & P188788 Schultz 4215 N NSG Schultz 4515 N NSG NE 4758 N RR NSG SS Coop FFR 414 P188788 SS Coop RT 446 (RR) NSG SS Coop FFR-478 P188788 Stewart SB 4490 P188788 Stewart SB 4640 P188788 & Peking Stewart SB 466R (RR) P188788 Stine 4322 P188788 Stine 4562 P188788 Stone SE-4397 N NSG Terra TS 4292 P188788 Terra TS 466 RR NSG Terra TS 4792 P188788 Terral TV 4479 P188788 Terral TV 4770 P188788 Trisler Trisoy 4064 NSG Trisler Trisoy 4212 NSG Trisler Trisoy 4432 NSG VanHorn VH 4340 N NSG Wildy WS EX 52 NSG Wildy WS 4305 NSG Wildy WS 4505 NSG Wildy WS 4845 NSG RESISTANT VARIETIES MATURITY GROUP V AgVenture AV 1504 NSG Asgrow A5403 Peking & P188788 Asgrow A5545 NSG Asgrow A5547 P188788 & Peking Asgrow A 5704 P188788 & Peking Asgrow A5801 RR P188788 & Peking Asgrow A5843 P188788 & Peking Asgrow A5848 P188788 & Peking Asgrow AG5951 RR P188788 & Peking Asgrow A 5959 P188788 & Peking Callahan 5510 P188788 DeKalb CX 510 C P188788 DeKalb CX 570 C NSG Delta Pine DP 3519 S P188788 Delta Pine DP 5352 P188788 & Peking Delta Pine DP 5644 RR P188788 & Peking Delta Pine DP 3588 Peking & P188788 Delta Pine 5806 RR P188788 & Peking Delta Pine DP 5960 RR P188788 & Peking Delta Pine DP 3571 S P188788 Delta Pine DP 415 Peking Gateway 511 Peking Golden Harvest H-1500 P188788 Great Lakes GL5123 P188788 Growmark HS 5199 P188788 Growmark HT 551 STS P188788 Gutwein 7525 C NSG Gutwein 7530 C NSG Hartz H 5218 Peking Hartz H 5545 Peking Hartz H 5545 (RR) Peking Hartz H 5350 P188788 Hartz 5350 (RR) P188788 Hartz H 5164 (RR) P188788 Hartz H 5566 (RR) P188788 Hartz H 5088 Peking Hartz H 5088 (RR) Peking Hartz H 5488 Peking Hornbeck HBK 5149 NSG Hornbeck SB HBK R5411 (RR) NSG Hornbeck SB HBK R5588 NSG Hornbeck HBK 54 NSG Hornbeck HBK 5770 NSG Hornbeck HBK 58 NSG LG Seeds JMS 5009C Peking MFA Morsoy 9152 SCN P188788 NC + 5A15 P188788 NC + 5A44 P188788 NC + 5A45RR (RR) P188788 Novartis (Ciba) 3505 Peking Novartis (NK) S57-11 P188788 & Peking Novartis (NK) S59-V6 (RR) P188788 Novartis (NK) S59-60 P188788 & Peking Patriot 537 N P188788 Patriot 555 N P188788 Pioneer 9521 Peking Pioneer 9552 P188788 Pioneer 9584 Peking Pioneer 9593 Peking (Public, KS) KS 5292 Peking (Public, MO) Hartwig P1437654 & Peking (Public, MO) Delsoy 5500 Peking & P188788 (Public, MO) Rhodes P188788 (Public, MS) Bedford Peking & P188788 (Public, MS) Forrest Peking (Public, TN) TN 5-95 P188788 & Peking Schultz 5015 N NSG SS Coop RT 540 (RR) NSG SS Coop FFR-542 NSG SS Coop FFR-595 P188788 Terra TS 504 Peking Terral TV 5495 Peking Terral TV 5797 Peking Terral TV 5893 P188788 Terral TV 5926 P188788 Trisler Trisoy 5170 NSG RESISTANT VARIETIES MATURITY GROUP VI Asgrow AG6101 RR P188788 & Peking Asgrow A6297 P188788 & Peking Asgrow A6711 P188788 & Peking Asgrow A6961 P188788 & Peking Delta Pine DP 3640 P188788 Delta Pine DP 3681 Peking Hartz H 6104 Peking Hartz H 6200 Peking Hartz H 6686 (RR) NSG Hornbeck HBK 6600 P188788 Hornbeck HBK 67 NSG Novartis (NK) S60-E4 (RR) P188788 & Peking Novartis (NK) S62-62 P188788 Novartis (NK) S65-50 P188788 & Peking Novartis (NK) S67-70 P188788 & Peking Pioneer 9692 Peking (Public, TN) TN 6-90 Peking Terral TV 6253 Peking Terral TV 6792 Peking Terral TV 6696 P188788 RESISTANT VARIETIES MATURITY GROUP VII Delta Pine DP 3733 P188788 Hartz H 7440 P188788 Hartz H 7550 (RR) Peking Hornbeck HBK 79 NSG Novartis (NK) S73-Z5 (RR) Peking & P188788 Novartis (NK) S75-55 P188788 & Peking Pioneer 9711 Peking Pioneer 9761 Peking Pioneer 97B61 P188788 RESISTANT VARIETIES MATURITY GROUP VIII Novartis (NK) S83-30 Peking Novartis C 6738 Peking

Examples of SCN susceptible varieties are shown in Table 33. TABLE 33 AgriPro Seeds Inc., Ames, IA (515-232-0891) AP1953, AP1995, AP2220, AP25985, AP2995, AP3250, AP3414, AP3616, AP3868, AP2880 Albert Lee Seed Housn, Albert Lee, MN (507-373-3181) 1796, 2397 Callahan Seeds, Westfield, IN 9317-896-5551) 6330, 7221x, 7250x, 7317, 7383, 8200x, 8275, 8363 Cenex/Land O'Lakes, Fort Dodge, IA (515-576-7311) L2126, L2646, L2779 Crow's Hybrid Com Co., Milford, IL (615-889-4151) 19001, 20001, EX0222, 25005, 28003, 32003, 33003, EX0426, EX0536, 38004, 30007 Custom Farm Seed, Momence, IL (815-472-2433) CFS215, CFS290 Dairyland Seed Company, Inc., West Bend, WI (800-236-0163) DSR-173, DSR-180/STS, DSA-195, DSA-220/STS, DSR-220/STS, DSR-246/STS, DSA-271/RR, DSR-277, DSR-293/RR, DSA-300, DSR-325, DSR-314/STS Dale Ewing Seed, Jewell, IA (515-827-5114) 165, 170, 199, 202, 230RX, 241R, 244, 250, 255, 260+, 265, 270 DeKalb Genetics Corporation, DeKalb, IL (815-756-7333) CX197, CX205, CX212, CX228, CX229, CX232, CX252, CX267, CX278, CX289, CX313, CX314, CX351, CX368, CX377, CX399 Dennis Ewing Farm Seed, Ames, IA (515-732-6236) 1991, 2162, 2221, 2221*, 2404, 2535, 2625, 2729, 2727*, 2727B, 2777, 2808*, 2818*, 2088, 3000, 3132, 3132*, 3230, 3424A, 3454, 3505B, 3550B, 3777, 3919, 4040*, D34Exp, D18Exp Domestic Seed & Supply, Inc., Madison, SD (605-256-6529) M 1190, M 2200, M 2259, M 2270 Farm Aventage, Clarion, IA (515-825-3682) FA 1924, FA 2065, FA 2177, FA 2477, FA 2486, FA 2532, FA 2743 Fontanelle Hybrids, Nickerson, NE (402-721-1410) 2232, 3303, 3373 Four Star Seed Co., Parkersburg, IA (319-346-2162) 4266, 4267, 4270A, 4334, 4450K Garst Seed Company, Slater, IA (515-585-3574) Ex7173, D180, EX7265, EX7224, 0260, 0308, D331, EX7346, EX7357 GMA Seed Co., Old Lyme, CT (860-434-7999) SV13020 Gold Country Seed, Inc., Norwood, MN (612-467-4320) Odin, X3719, X3721, X5622, Golden Seed Co., Cordova, IL (800-421-1156) JC Robindson Seed Co., Waterloo, NE (800-228-9906) H1184, H1190, H1194, H1211, H1218, H1237, H1236, H1269, H1279, H1295, H1315, H1353, X214, X282 Great Lakes Hybrids, Ovid, MI (617-834-2251) GL1872, GL2334, GL2415, GL, 2772, GL2818, GL3101 Growmark Inc., Bloomington, IL (309-557-6399) HS2171, 215, HT221, HS2561, HS2861, HS3071, 3251, HS3362 Hills Seed Co. Ellsworth, IA (515-836-2141) EX238, EX248, EX268, EX278, HS1960, HS2170, HS2270, HS2570, HS259, HS2860, HS2970, HS3260, HS3360 Hoegemeyer Hybrids, Hooper, NE (402-654-3399) 191, 202, 225, 253, 312, 365, 380 Hy-Vigor Sands, Pauline, IA (712-448-2187) 2025, EX: 203, 2350, 2375, 2400, 3990 Illinois Ag. Exp. Stn., Urbana, IL Bell, Carsay79, Iroquois, Jack, Macon, WilliamsBZ Indiana Ag. Exp. Stn., West Layfette, IN Probst Iowa Ag. Exp. Stn., Ames, IA Archer, HP204, IA1005, IA1006, IA1007, IA2007R, IA2008R, IA2011, IA2012, IA2013, IA2016, IA2017, IA2018, IA2019, IA2020, IA2021, IA2022, IA2034, IA2035, IA2036, IA2037, IA3001, IA3002, IA3004, IA3005, IA3006, IA3008, IA3009, Kenwood94, LS301, Marcus95, Pella86, VintonB1 Jacobsen Hybrid Corn Co. Inc., Lakeview, IA (712-657-2841) J659, J679, J750, J756, J772, J774, J777, J844, J859, J865, J876, J956, J960, J971 Kaltenberg Seed Farms, Waunakee, WI (800-383-3276) KB208, KB214, KB225, KB245, KB259, KB366 Caup Seed Co., West Point, NE (402-372-5588) 23344, 2451, KS1977, KS2474, KS2685, KS2774, KS2865, KS2887, KS2977, KS3287, KS3464 Kruger Seed Co., Dike, IA (800-772-2721) K-1777, K-1990, K-1990*, K-2021*, K-2025, K-2343*, K-2425, K-2425, K-2525, K-2535*, K-2625*, K-2625, K-2725, K-2727*, K-2828, K-3032*, K-S032, K-3040, K-3222, K-3232*, K-3424, K-3505, K-3525E, K-3525, K-3535*, K-3737, K-3777, K-3939*, {circumflex over ( )}21 RR Ex, {circumflex over ( )}242Roundup, {circumflex over ( )}25 RR Ex, {circumflex over ( )}28 RR Ex, {circumflex over ( )}36 RR Ex, {circumflex over ( )}36+ RR Ex KSC/Challenger Sd Company, Cedar Falls, IA (319-989-2256) K-2545 Latham Seed Co., Alexander, IA (515-692-3258) 250 Brand, 392 Brand, 410 Brand, 590 Brand, 621 Brand, 660 Brand, 662 Brand, 680 Brand, 720 Brand, 841 Brand, 950 Brand, 962 Brand, 1140 Brand, EX-324STS, EX-330, EX-420, EX-640, EX-710, EX-730 Lewis Hybrids Inc., Ursa, IL (217-964-2131) 310, 322, 360, 363, 390 LG Seeds, Mount Pleasant, IA (319-385-2299) LG6212, LG6236STS, LG6245, LG6288, LG6339, LG6369 Maple Leaf Foods Intl., Toronto, Ontario (416-480-6420) WJ130563 Mark Seed Co., Perry, IA (800-383-6275) EX823, EX824, EX921, MRK9519, MRK9533, MRK9632, MRK9721, MRK9721-4, MRK9721-9, MRK9727-S, MRK9732, MRK9733, MRK97CN33, MRK9825, MRK9825-5, MRK9826, MRK9826-0, MRK9826-7, MRK9827, MRK9827-5, MRK9827-7, MRK9828, MRK9829, MRK9833, MRK9926, MRKEX835, MRKEX9333 Mels Seed & Feed, Lemars, IA (712-548-4131) GM2810, GM2640 Mellow Dent Seed, Alla, IA (712-296-3663) Coop Seed, Alla, IA (712-756-3663) 1289, 6191, 6221, 6231, 0244, 6251, 6252, 6292, 5333, 5334, 6335, 6361 Merschman Seeds, Westpoint, IA (319-837-8711) MarsIV, ApacheV, CheyenneV, MoheganII, MohaveIII, ChickasawIII, HarrisonIV, TrumanV, FillmoreIV, EisenhowerIV, MadisonV, Midland Soybean Development Assoc., Garden City, MO (816-852-8203) 94, 92, 9435, 9536, 9733*, RR2351 Midwest Seed Genetics Inc., Carroll, IA (800-369-8215) G-1885, G-1912, G-1930, G-2112, G-2440, G-2454, G-2519, G-2818, G-2910, G-3141, G-3242, G-3300, G-3410, G-3626, G-3996 Minnesota Ag. Exp. Stn., St. Paul, MN Parker, Sturdy Mitchell Seeds, Buckingham, IA (319-478-8598) 2596 Mycogen Seeds, St. Paul, MN (800-Mycogen) 200, 5205, 5251, 5318, 5337, 5348 Naylor Seed Co., Scotch Grove, IA (800-747-7333) NS1980, NS2150, NS2170, NS2250, NS2270, NS2380, NS2480, NS2470, NS2670, NS2685STS, NS2750, NS2755STS, NS2770, NS3380, NS3470 NC+ Hybrids, Lincoln, NE (402-467-2517) 1A88, 2A15, 2A22, 2A42, 2A70, 2A99, 3A26, 3A44, 3A67 Nebraska Ag. Exp. Stn., Lincoln, NE NE2596, NE3396, NE3297, Nemaha, Odell Novartis Seeds Inc., Minneapolis, MN (812-593-7333) S19-90. S24-92, S30-06 Ohio Ag. Res. Development Str., Wooster, OH Century84, Charleston, Resnik Ottilie RO Seed, Marshalltown, IA (515-753-5561) 8200, 8206, 8222, 8250, 8262, 8272, 8299, 8320, 8333, 8350, 375 Patriot Seed Co., Bowen, IL (217-842-5612) 188, 192, 196, 208, 210N, 233, 238, 251, 258, 280, 288, 298, 303, 308, 321, 330 Pioneer Hi-Bred Intl., Des Moines, IA (515-253-9570) 9172, 9204, 9233, 9245, 9254, 9281, 92852, 92891, 9304, 9306, 9321, 9342, 9343, 9352, 93A1, 9350, 93B41, 93882 Prairie Brand Seed Co., Story City, IA (800-544-8751) PB-192, PB-194, PB-197, PB-201, PB-202, PB-210, PB-2120, PB-212E, PB-216X, PB-218X, PB-220X, PB-227, PB-235X, PB-236, PB-237X, PB-242X, PB-246, PB-255X, PB-257X, PB-264E, PB-265X, PB-266+, PB-271X, PB-2720, PB-276, PB-288, PB-293, PB-296, PB-303, PB-322, PB-326X, PB-330, PB-335, PB-337, PB-339X, PB-345, PB-346, PB-353, PB-358, PB-363, PB-382, PB-384, PB-SP19C, PB-SP20M, PB-SP21, PB-SP22M, PB-SP23, PB-SP26, PB-SP27, PB-SP28, PB-Sp29, PB-SP34, PB-SP36, PB-SP38 Producers Hybrids, Battle Creek, NE (402-675-2975) 2151, 2451, 3051, 3251, 3651, Ex6127 Profiseed Inc., Hampton, IA (515-456-4791) 1997, 2000, 2000+, 2035, 212, 2413, 2556, 2605, 2705, 2898, X197, X240 Ramy Int. Ltd., Mankato, MN (800-658-7269) 1995, 2097, 2195, 2220, 2395, 2420, 2450, 2550, 2555, 2650, 2800 Renk Seed Co., Sun Prairie, WI (608-837-7351) RS1898, RS1990, RS2334, RS2595, RS2797 Renze Hybrids Inc., Carroll, IA (712-559-3301) R1996, R1998, R2098, R2297, R2397, R2496, R2597, R2698, R2797, R2796, R2996, R3097, R3297, R3596, R3698 Rolling Meadows Inc., Charter Oak, IA (712-678-3581) RM9628, RM9722, RM9727, RM9730 Sand Seed Service Inc., Mercus, IA (712-376-4135) *EXP2001, EXP2501, EXP2501, *EXP3530, *EXP9632, EXP9626, EXP9631A, EXP9633, *EXP9722, *EXP9727, EXP9728, *EXP9730, *EXP9734, EXPC301, EXPS1816, SOI169, SOI260. SOI275, SOI277, SOI353, SOI371, SOI386 Stine Seed Co., Adel, IA (515-677-2505) 1970, 1980, *2180, 2250, *2480, *2488, 2500, 2621, 2671, *2680, 2686, *2788, 2870, 3100, 3171, *3290, 3380, 3400, *3581, 3660, *3683, 3870, 3883 Terra Int. Inc., Sioux City, IA (712-233-3609) E147, E250, E267, E277, E317, E364T, E387, TS174, TS194, TS200, TS203, TS247STS, TS253, TS265, TS315, TS364, TS415 Thompson Agronomics, Leland, IA (515-567-3350) EX5125, EX5315, EX5423, EX5704, EX5308, EX6245, EX6714, EX7117, EX7237, EX7418, EX7537, EX7707, EX7730, T-3229, EX5416, EX5705, EX8754, EX7733, EX7735, EX7779, T-3193, T-3212, T-3217, T-3222, T-3227, T-3251, T-3264, T-3310 Treley Inc., Livingston, WI (505-543-6363) 156 Brand, 196 Brand, 226 Brand, 246 Brand UAP Seed Co., Independence, IA (319-334-6898) 3188, 3195A, *3202, 3233, 3256, 3262, 3304, 3315, *3331N, *3367A, 3368 Wilson Seeds Inc., Harlan, IA (712-755-3841) 2136, 2563, 2780, 3110, 3380

Although only exemplary embodiments of the invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims. 

1.-16. (canceled)
 17. A method of controlling cyst nematode population in soybeans, comprising the steps of: providing a quantity of a first cyst nematode race resistant soybean variety having resistance to a first race spectrum; providing a quantity of a second soybean variety selected from the group consisting of a cyst nematode race resistant soybean variety having resistance to a second race spectrum and a cyst nematode susceptible soybean variety; blending the first and second soybean varieties to achieve a first blended composition; planting said first blended composition to yield a soybean crop; and rotating the growing of said first blended composition of resistant varieties with the growing of a second blended composition of resistant and susceptible varieties over at least two growing seasons. 18.-19. (canceled)
 20. The method of claim 17, further including the steps of providing a quantity of a third cyst nematode race resistant soybean variety having resistance to a third race spectrum, and blending the first, second and third soybean varieties to achieve the first, second or both blended composition.
 21. (canceled)
 22. The method of claim 20, wherein a blended composition of resistant varieties is grown for at least two consecutive growing seasons followed by growing a blended composition consisting of resistant and susceptible varieties.
 23. The method of claim 17, wherein said rotating includes growing at least one alternate crop.
 24. The method of claim 23, wherein said alternate crop is selected from the group consisting of corn, alfalfa, oats, clover, sorghum, cotton, canola, forage grasses, sunflowers and rice, a non-blended susceptible soybean variety and a non-blended resistant soybean variety. 25.-26. (canceled)
 27. The method of claim 22, wherein said rotating includes growing at least one alternate crop.
 28. The method of claim 27, wherein said alternate crop is selected from the group consisting of corn, alfalfa, oats, clover, sorghum, cotton, canola, forage grasses, sunflowers, rice, a non-blended susceptible soybean variety and a non-blended resistant soybean variety.
 29. A blended composition produced by the method of claim
 17. 30. A blended composition produced by the method of claim
 20. 31. (canceled)
 32. The method of claim 17, wherein said rotating consists of growing a CTB soybean blend the first growing season, growing a CTA soybean blend the second growing season, growing a CTB soybean blend a third growing season and growing a CTA soybean blend a fourth growing season.
 33. The method of claim 17, wherein said rotating consists of growing a CTA soybean blend a first growing season, growing a CTB blend a second growing season, and growing a CTA soybean blend a third growing season. 